Importing animations for Rigify in Blender for use in Unity
In the unity asset store, there is a seller named Mixamo. They have an animation store that sells mecanim animations, like a run cycle for $10 each.

https://www.assetstore.unity3d.com/#/content/362

Here is a short demo of it:
http://www.youtube.com/watch?v=17V3_j1NZhM

As far as I know, you have to use mecanim (the new and improved animation system in unity).

With the Mixamo animation store you can download and preview the animations on any character. But the names on the bones have to be right. I'm not entirely sure if rigify does this right, should be a minor problem compared to making all those animations.

Edit:
Oups, according to this page:
http://meglassons.com/?page_id=1971
Rigify isn't compatible with mechanim. You have to rename the bones or create the rig yourself.